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CMPT 120
Topic: Introduction to Python and
Demo of Software Development Process
Learning outcomes
At the end of this course, a student is expected to:
• Describe and apply fundamental concepts and
terminology:
• Execution flow
• Create (design) small size programs using Python:
• Hand trace code (programs) and predict results of
executing code
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Last Lecture
• Defined programming languages and their evolution (first 3
generations)
• Described compiler and interpreter
• Introduced to Scratch
• Demo’ed of the Problem Solving Process using Scratch
Step 4
Step 2
Step 1
Step 5
Implement
Design algorithm
State
Test it
algorithm
+ Identify data
problem
into computer
Problem/task
Algorithm
program
Cat
walking in
a square?
Story: cat walks in a square
In more details:
repeat 4 times
cat walk 50 steps right
then turn clockwise 90o
Computer program
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Today’s Menu
• i-clicker Session 1
• Introduce Python
• Practice the Problem Solving Process some
more using Python
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Let’s introduce Python
• We shall use Python 3 (as opposed to Python 2)
• Where to find Python?
• What is Python?
• “Python is an text-based, interpreted, object-oriented,
dynamically-typed, high-level programming language
…”
Inspired from https://www.python.org/doc/essays/blurb/
• Why Python?
• Can be used on many platforms:
• Windows, MAC OS, Linux
• Powerful, yet easy to learn, use, read and debug 
• Syntax emphasizes readability
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How to use Python IDLE
• 2 ways of using Python IDLE:
1. Python Interpreter Shell
• Workflow:
• Write one statement of Python @ a time
• Wait a minute! What is a “statement”? 
• Press Enter
• The Python Interpreter makes sure the statement
does not contain any error
• Then it executes (interprets) the statement typed
• And outputs the result
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How to use Python IDLE
• 2 ways of using Python IDLE:
2. Python Program Editor
• Workflow:
• Create a new program OR open an already
existing program
• Write code into the program
• Save the program
• Execute the whole program:
• The Python Interpreter makes sure the program does
not contain any error
• Then it executes (interprets) the statements in the
program
• And outputs the result
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Demo –
Step 1 - Problem Statement
• Let’s figure out our course final grade
• More specifically, the activities of our course are
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Assignment 1
Assignment 2
Assignment 3
Assignment 4
Midterm
Final exam
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Demo – Step 2 - Solution (Algorithm)
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Set finalGrade to 0
Input gradeAssn1
Input gradedOutOfAssn1
Input percentOfFinalGradeAssn1
Compute newGradeAssn1 -> gradeAssn1 * percentOfFinalGradeAssn1 / gradedOutOfAssn1
finalGrade = finalGrade + newGradeAssn1
Input gradeAssn2
Input gradedOutOfAssn2
Input percentOfFinalGradeAssn2
Compute newGradeAssn2 -> gradeAssn2 * percentOfFinalGradeAssn2 / gradedOutOfAssn2
finalGrade = finalGrade + newGradeAssn2
Input gradeAssn3
Input gradedOutOfAssn3
Input percentOfFinalGradeAssn3
Compute newGradeAssn3 -> gradeAssn3 * percentOfFinalGradeAssn3 / gradedOutOfAssn3
finalGrade = finalGrade + newGradeAssn3
Input gradeAssn4
Input gradedOutOfAssn4
Input percentOfFinalGradeAssn4
Compute newGradeAssn4 -> gradeAssn4 * percentOfFinalGradeAssn4 / gradedOutOfAssn4
finalGrade = finalGrade + newGradeAssn4
Input gradeMT
Input gradedOutOfMT
Input percentOfFinalGradeMT
Compute newGradeMT -> gradeMT * percentOfFinalGradeMT / gradedOutOfMT
finalGrade = finalGrade + newGradeMT
Input gradeFE
Input gradedOutOfFE
Input percentOfFinalGradeFE
Compute newGradeFE -> gradeFE * percentOfFinalGradeFE / gradedOutOfFE
finalGrade = finalGrade + newGradeFE
Print finalGrade
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Demo – Step 4 - Implement
Algorithm into Program
• Let’s write some code!
• Then, let’s illustrate:
• Execution flow
• Hand tracing our code
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Demo – Step 5 - Testing
• How to test our program?
• Does our program execute?
• Does it solve our initial problem?
• Test Case
1. Test Data:
2. Expected Results:
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Summary
• i-clicker Session 1
• Introduce Python
• Practice the Problem Solving Process some more
using Python
Step 1
State
problem
Step 2
Design algorithm
+ Identify data
Step 4
Implement
algorithm
into computer
program
Step 5
Test it
12
Next Lecture
• Start learning Python’s building blocks
• Variables
• Values
• Types
• and Literal values
• Continue illustrating
• Execution Flow
• Hand tracing
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